Rats are able to move their heads to the beat of music, demonstrating for the first time in animals the innate synchronization of rhythms.

Moving precisely to the beat of music was considered an intrinsically human skill. But new research shows that rats also have this ability. The optimal rhythm for nodding depended on the brain’s time constant (the speed at which our brain can respond to something), which was similar across species. This means that the ability of our auditory and motor systems to interact and translate to music may be more widespread across species than previously thought. This new discovery offers a deeper insight not only into the spirit of animals, but also into the origins of our own music and dance.

Can you move to the beat or do you have two left feet? It appears that how we time our movement with music depends somewhat on our innate genetic ability, an ability previously thought to be a uniquely human trait. Although animals also respond to auditory sound, can produce rhythmic sounds, or are trained to respond to music, this is not the same as the complex neural and motor processes that allow them to naturally recognize the rhythm of song. or even predict. This is called beat synchronicity.

Research studies (and home videos) have only relatively recently shown that some animals share our desire to move in a groove. A new paper from a team at the University of Tokyo proves that rats are one of them. Associate Professor Hirokazu explained: “Rats exhibit innate synchronization – that is, without any prior training or exposure to music – synchronization of beats between 120 and 140 bpm (beats per minute). Takahashi. From the Graduate School of Information Science and Technology. “The Voice of Our Brain The processing area of ​​the auditory cortex was also adapted to 120-140 beats/minute, which we were able to explain using a mathematical model of brain adaptation.

So why play music to rats in the first place? “Music has a powerful effect on the brain and has a profound effect on emotion and cognition. To use music effectively, we need to discover the neural mechanism underlying this empirical fact,” said Takahashi. “I’m also a specialist in electrophysiology, which looks at electrical activity in the brain, and I’ve studied the rat auditory cortex for many years. »

The team had two alternative hypotheses: the first was that the optimal music tempo for beat synchrony would be determined by the body’s time constant. It varies between species and is faster for small animals than for humans (think how quickly a rat knocks itself down). The second was that the optimal pace was instead determined by a brain time constant that was surprisingly similar across species. “Following our study with 20 human participants and 10 rats, our results show that the optimal tempo for beat synchronization depends on the time constant in the brain,” Takahashi said. “This demonstrates that the animal brain can be useful in elucidating the mechanisms of music perception. »

The rats were fitted with miniature wireless accelerometers capable of measuring the smallest head movements. Human participants also wore accelerometers in headphones. They were then played one-minute excerpts from Mozart’s Sonata for Two Pianos, K. 448, at four different tempos: seventy-five percent, 100 percent, 200 percent, and 400 percent of the speed. The original tempo is 132 bpm, and the results showed that the rats’ beat synchronization was most evident in the 120-140 bpm range. The team also found that rats and humans bobbed their heads at the same rate to the beat, and that the level of head bobbing decreased as the music sped up.

“To our knowledge, this is the first report of innate beat synchronization in animals that is not achieved by training or exposure to music,” Takahashi said. “We also hypothesized that short-term adaptation in the brain is involved in the regulation of beats in the auditory cortex. We were able to explain this by fitting our neural activity data to a mathematical model of adaptation. Moreover, our adaptation model showed that in response to a random click sequence, the highest beat prediction performance occurred when the mean interstimulus interval (the time between the end of one stimulus and the beginning of the next) was about 200 milliseconds (one thousandth of a stimulus). the second). Internote intervals in classical music show that the brain’s adaptive feature is at the heart of music perception and creation. »

Researchers see it as an interesting insight into the animal spirit and the development of our own rhythmic synchronicity, but also into the creation of music itself. “Then I would like to reveal how other musical features, such as melody and harmony, are related to brain dynamics. I am also interested in how, why, and which brain mechanisms create cultural domains such as visual arts, music, science, technology, and religion,” said Takahashi. “I believe this question is the key to understanding how the brain works and developing a new generation of AI (artificial intelligence). Also, as an engineer, I am interested in using music for a happy life. »

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Provided by Materials University of Tokyo. Note: Content may be edited for style and length.

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